Heat oil in a large skillet over medium high heat.
In a large bowl, whisk together flour and seasoned salt.
Gradually add beer, one cup at a time, whisking to avoid lumps. Batter should be the consistency of pancake batter. Adding less beer will produce a thicker crust while adding more beer with add a thinner coating.
Add raw onion rings to the batter. Stir several times to ensure an even coating.
Drop a single ring into the oil as a test. If the oil begins to bubble rapidly, you are ready to begin frying. Reduce heat to medium to prevent rings from browning to quickly.
Working in batches, add rings to the skillet, trying not to allow rings to touch. Fry for about 3-5 minutes, turning once, until rings are golden brown.
Drain on paper towels.
Sprinkle with table salt and black pepper if desired.
Storage. Allow onion rings to cool completely. Line a plastic freezer bag with paper towels to absorb any excess grease and moisture, then seal the bag and store in the fridge. Consume within five days.Freezing. I do not recommend freezing leftover onion rings. Freezing and thawing will change the texture of the onions and cause them to become mushy.Reheating. Preheat the oven to 350 degrees F. Place the onion rings in a single layer on rack over a foiled lined baking sheet. Bake for 5-10 minutes until the onion rings are crisp again and heated thorough.